2026 ICD-10-CM Diagnosis Code S31.65AA
Open bite of abdominal wall, unspecified flank with penetration into peritoneal cavity, initial encounter
- ICD-10-CM Code:
- S31.65AA
- ICD-10 Code for:
- Open bite of abd wall, unsp flank with penet perit cav, init
- Is Billable?
- Yes - Valid for Submission
- Code Navigator:
S31.65AA is a billable diagnosis code used to specify a medical diagnosis of open bite of abdominal wall, unspecified flank with penetration into peritoneal cavity, initial encounter. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2025 through September 30, 2026.
S31.65AA is an initial encounter code, includes a 7th character and should be used while the patient is receiving active treatment for a condition like open bite of abdominal wall unspecified flank with penetration into peritoneal cavity. According to ICD-10-CM Guidelines an "initial encounter" doesn't necessarily means "initial visit". The 7th character should be used when the patient is undergoing active treatment regardless if new or different providers saw the patient over the course of a treatment. The appropriate 7th character codes should also be used even if the patient delayed seeking treatment for a condition.
Unspecified diagnosis codes like S31.65AA are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.
Coding Guidelines
The appropriate 7th character is to be added to each code from block Open wound of abdomen, lower back, pelvis and external genitals (S31). Use the following options for the aplicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
New 2026 ICD-10-CM Code
S31.65AA is new to ICD-10-CM code set for the FY 2026, effective October 1, 2025. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2025. This is a new and revised code for the FY 2026 (October 1, 2025 - September 30, 2026).
Code Edits
The Medicare Code Editor (MCE) detects errors and inconsistencies in ICD-10-CM diagnosis coding that can affect Medicare claim validity. These Medicare code edits help medical coders and billing professionals determine when a diagnosis code is not appropriate as a principal diagnosis, does not meet coverage criteria. Use this list to verify whether a code is valid for Medicare billing and to avoid claim rejections or denials due to diagnosis coding issues.
Unspecified codes
Unspecified codes exist in the ICD-10-CM classification for circumstances when documentation in the medical record does not provide the level of detail needed to support reporting a more specific code. However, in the inpatient setting, there should generally be very limited and rare circumstances for which the laterality (right, left, bilateral) of a condition is unable to be documented and reported. The following pages contain the list of unspecified ICD-10-CM diagnosis codes for which there is a more specific code to identify laterality (right, left, bilateral) within that code family.
Replacement Code
S3165AA replaces the following previously assigned ICD-10-CM code(s):
- S31.659A - Open bite of abd wall, unsp quadrant w penet perit cav, init
Code History
- FY 2026 - Code Added, effective from 10/1/2025 through 9/30/2026
